Issue 7030046: code review 7030046: cmd/6g, cmd/8g: Allow optimization of return registers.

Issue 7030046: code review 7030046: cmd/6g, cmd/8g: Allow optimization of return registers. (Closed)

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Created:
12 years, 6 months ago by DMorsing

Modified:
12 years, 6 months ago

Reviewers:

CC:
dave_cheney.net, rsc, golang-dev

Visibility:
Public.

Description

cmd/6g, cmd/8g: Allow optimization of return registers. The peephole optimizer would keep hands off AX and X0 during returns, even though go doesn't return through registers.

Patch Set 1 #

Patch Set 2 : diff -r 88ae367d61aa https://code.google.com/p/go/ #

Patch Set 3 : diff -r 88ae367d61aa https://code.google.com/p/go/ #

Patch Set 4 : diff -r e8cfa948baf2 https://code.google.com/p/go/ #

Created: 12 years, 6 months ago

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		Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+0 lines, -4 lines)			Patch
	M	src/cmd/6g/peep.c	View	1	1 chunk	+0 lines, -2 lines	0 comments	Download
	M	src/cmd/8g/peep.c	View	1 2 3	1 chunk	+0 lines, -2 lines	0 comments	Download

Messages

Total messages: 6

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DMorsing

Hello golang-dev@googlegroups.com (cc: golang-dev@googlegroups.com), I'd like you to review this change to https://code.google.com/p/go/

12 years, 6 months ago (2012-12-30 20:09:59 UTC) #1

dave_cheney.net

Hello, Can you provide some before/after asm samples ? Cheers Dave On Mon, Dec 31, ...

12 years, 6 months ago (2012-12-30 21:43:01 UTC) #2

DMorsing

On Sun, Dec 30, 2012 at 10:43 PM, Dave Cheney <dave@cheney.net> wrote: > Hello, > ...

12 years, 6 months ago (2012-12-30 22:25:23 UTC) #3

On Sun, Dec 30, 2012 at 10:43 PM, Dave Cheney <dave@cheney.net> wrote:
> Hello,
>
> Can you provide some before/after asm samples ?
>
> Cheers
>
> Dave
>

package foo

type X struct {
        X, Y, Z float64
}

var y = 2

func bar() X {
        x := X{
                float64(y),float64(y),float64(y),
        }
        return x
}

before:
--- prog list "bar" ---
0000 (/home/daniel/src/test/test.go:9) TEXT    bar+0(SB),$0-24
0001 (/home/daniel/src/test/test.go:9) MOVQ    y+0(SB),AX
0002 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+0(SB),X0
0003 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+8(SB),X0
0004 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+16(SB),X0
0005 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
0006 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X3
0007 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
0008 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X2
0009 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
0010 (/home/daniel/src/test/test.go:13) MOVSD   X3,.noname+0(FP)
0011 (/home/daniel/src/test/test.go:13) MOVSD   X2,.noname+8(FP)
0012 (/home/daniel/src/test/test.go:13) MOVAPD  X1,X0
0013 (/home/daniel/src/test/test.go:13) MOVSD   X1,.noname+16(FP)
0014 (/home/daniel/src/test/test.go:13) RET     ,

after:
--- prog list "bar" ---
0000 (/home/daniel/src/test/test.go:9) TEXT    bar+0(SB),$0-24
0001 (/home/daniel/src/test/test.go:9) MOVQ    y+0(SB),AX
0002 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+0(SB),X0
0003 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+8(SB),X0
0004 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+16(SB),X0
0005 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
0006 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X3
0007 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
0008 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X2
0009 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
0010 (/home/daniel/src/test/test.go:13) MOVSD   X3,.noname+0(FP)
0011 (/home/daniel/src/test/test.go:13) MOVSD   X2,.noname+8(FP)
0012 (/home/daniel/src/test/test.go:13) MOVSD   X1,.noname+16(FP)
0013 (/home/daniel/src/test/test.go:13) RET     ,

Note instruction 12 on the before listing. This move was not optimized
away because the peephole opt pass thought X0 was the return register.

dave_cheney.net

Excellent. This was a problem in 5g that minux and I had been discussing since ...

12 years, 6 months ago (2012-12-30 22:26:07 UTC) #4

Excellent. This was a problem in 5g that minux and I had been
discussing since September.

https://codereview.appspot.com/7030047/

On Mon, Dec 31, 2012 at 9:25 AM, Daniel Morsing
<daniel.morsing@gmail.com> wrote:
> On Sun, Dec 30, 2012 at 10:43 PM, Dave Cheney <dave@cheney.net> wrote:
>> Hello,
>>
>> Can you provide some before/after asm samples ?
>>
>> Cheers
>>
>> Dave
>>
>
> package foo
>
> type X struct {
>         X, Y, Z float64
> }
>
> var y = 2
>
> func bar() X {
>         x := X{
>                 float64(y),float64(y),float64(y),
>         }
>         return x
> }
>
> before:
> --- prog list "bar" ---
> 0000 (/home/daniel/src/test/test.go:9) TEXT    bar+0(SB),$0-24
> 0001 (/home/daniel/src/test/test.go:9) MOVQ    y+0(SB),AX
> 0002 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+0(SB),X0
> 0003 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+8(SB),X0
> 0004 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+16(SB),X0
> 0005 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
> 0006 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X3
> 0007 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
> 0008 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X2
> 0009 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
> 0010 (/home/daniel/src/test/test.go:13) MOVSD   X3,.noname+0(FP)
> 0011 (/home/daniel/src/test/test.go:13) MOVSD   X2,.noname+8(FP)
> 0012 (/home/daniel/src/test/test.go:13) MOVAPD  X1,X0
> 0013 (/home/daniel/src/test/test.go:13) MOVSD   X1,.noname+16(FP)
> 0014 (/home/daniel/src/test/test.go:13) RET     ,
>
> after:
> --- prog list "bar" ---
> 0000 (/home/daniel/src/test/test.go:9) TEXT    bar+0(SB),$0-24
> 0001 (/home/daniel/src/test/test.go:9) MOVQ    y+0(SB),AX
> 0002 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+0(SB),X0
> 0003 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+8(SB),X0
> 0004 (/home/daniel/src/test/test.go:10) MOVSD   statictmp_0000+16(SB),X0
> 0005 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
> 0006 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X3
> 0007 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
> 0008 (/home/daniel/src/test/test.go:10) MOVAPD  X1,X2
> 0009 (/home/daniel/src/test/test.go:10) CVTSQ2SD AX,X1
> 0010 (/home/daniel/src/test/test.go:13) MOVSD   X3,.noname+0(FP)
> 0011 (/home/daniel/src/test/test.go:13) MOVSD   X2,.noname+8(FP)
> 0012 (/home/daniel/src/test/test.go:13) MOVSD   X1,.noname+16(FP)
> 0013 (/home/daniel/src/test/test.go:13) RET     ,
>
> Note instruction 12 on the before listing. This move was not optimized
> away because the peephole opt pass thought X0 was the return register.

DMorsing

12 years, 6 months ago (2013-01-11 14:44:50 UTC) #6

*** Submitted as https://code.google.com/p/go/source/detail?r=da05833bf12e ***

cmd/6g, cmd/8g: Allow optimization of return registers.

The peephole optimizer would keep hands off AX and X0 during returns, even
though go doesn't return through registers.

R=dave, rsc
CC=golang-dev
https://codereview.appspot.com/7030046

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